Echinacea: Mixed results from recent trials

The research record on echinacea for the treatment and prevention
of colds paints a confusing picture, with tantalizing clues to
mechanisms of action and a combination of clinical and laboratory
evidence of immune system stimulation. The most recent studies
do little to clear the record, but present a mostly positive outcome.
Perhaps the most compelling conclusion to be drawn from a review
of the following three recent studies is that echinacea appears
to work more effectively when taken at the first sign of a cold
than when used as a daily preventative.

The first of these recent studies failed to support the use of
daily doses of echinacea extract for preventing the common cold
[Melchart et al., 1998]. In this double-blind, placebo-controlled
German clinical trial involving more than 300 healthy volunteers,
extracts of roots of Echinacea angustifolia DC, Asteraceae
and E. purpurea (L.) Moench were not significantly better
than placebo in preventing colds. The 12-week trial was intended
to test the prophylactic (preventive) effect of the two different
echinacea species against colds, with participants recruited from
four military sites and one factory. Over the course of the study,
each took 50 drops of echinacea extract (1:11, 30% alcohol) or
placebo twice a day from Monday to Friday, and recorded any cold
symptoms during the test. The two echinacea groups did experience
fewer colds, but the difference was too slight to be statistically
significant. In the placebo group, 37 percent caught colds, compared
to 32 percent of those taking E. angustifolia and 29 percent
of those taking E. purpurea. Although this result does
not meet the criteria for statistical significance, the authors
noted that echinacea may have provided a protective effect of
about 10 to 20 percent. They also noted that in other trials,
echinacea taken at the first sign of a cold significantly reduced
the number of people who developed a "full" cold and decreased
the duration of symptoms. Many echinacea users and herbalists
believe that using echinacea at the first sign of a cold is more
effective than long-term daily use. There are also questions concerning
the dosage used in this study. The 1:11 extract used by the researchers
is less than half the strength of the 1:5 extract used in the
often-cited 1992 study by Braunig et al., which demonstrated
that E. purpurea root had a significant effect on reducing
the duration and severity of colds and flu.

Another placebo-controlled, double-blind study offers a much
more positive outlook, based not on daily preventive echinacea
use but on an early intervention model [Brinkeborn et al.,
1998]. In this Swedish trial, 199 patients with colds took echinacea
extract or placebo at the first sign of a cold. Physicians judged
echinacea extract effective in 68 percent of cases, and 78 percent
of patients considered it effective. The hydroalcoholic extract
of fresh E. purpurea aerial parts (95%) and roots (5%)
was taken in doses of two tablets three times a day over a period
of eight days. The tablets contained a dosage of extract equivalent
to around 240 mg of echinacea per day. Patients and physicians
agreed that the preparation (Echinaforce®, Bioforce
AG, Switzerland) "resulted in a clearly greater reduction in clinical
symptoms than that seen with placebo."

This study, supervised by infectious disease specialist Dr. R.
Brinkeborn, was also significant in that it concentrated on volunteers
who considered themselves especially susceptible to colds. Patients
were instructed to begin taking the echinacea extract at the first
sign of a cold, and both patients and physicians evaluated effectiveness
on the basis of ratings of 12 specific cold symptoms. It should
be noted that placebo was judged effective by physicians in around
40 percent of cases and by patients in nearly 50 percent of cases.
However, the superior showing in the echinacea group was statistically
significant, and the authors concluded that echinacea "may be
recommended as well suited to the treatment of colds in the acute
stage."

Following a similar treatment protocol, a Swedish and German
research team reported positive results from the use of an echinacea
preparation (Echinagard®, Nature's Way, Utah) consisting
of squeezed sap of E. purpurea [Hoheisel et al.,
1997]. Sixty percent of those who took echinacea at the first
sign of a cold avoided developing full colds, and those who did
recovered quickly. In this randomized, double-blind, placebo-controlled
clinical trial, 120 patients with initial cold symptoms took 20
drops of the echinacea preparation every two hours for the first
day, and three times a day thereafter for up to 10 days. According
to patient evaluations, the symptoms progressed to a "real" cold
("i.e., fully expressed disease") in only 40 percent of those
taking echinacea, compared to 60 percent of those in the placebo
group. In addition to a 20 percent reduction in the numbers who
experienced "real" colds, those in the echinacea group who did
experience significant symptoms recovered from their colds twice
as fast (four days versus eight days in the placebo group).

This study included only persons especially susceptible to colds,
each having experienced three or more respiratory infections in
the six months before the study. The authors concluded that the
echinacea preparation tested "is a safe and effective therapy
when taken at the first signs of a common cold." - Rob McCaleb
(HRF)